Method of manufacture of a conductor rail

ABSTRACT

There is concerned a method of manufacture of a conductor rail comprising an aluminum body and a layer of more resistant for instance ferrous material attached thereto, whereby said layer is applied in liquid form suppressing an intermetallic layer of poor conducting properties usually obtained when uniting aluminum with ferrous and like materials.

United States Patent [191 Kugler et al.

[111 3,836,394 [4 1 Sept. 17,1974

3,148,086 Seibert 117/71 M 3,198,662 8/ 1 965 Seibert. 5,680 11/1966Dail 3,349, 10/1967 D 3,602, 8/1971 Sc 3,674,544 7/1972 3,679,460 7/197212/1972 Grosseau 117/9 4/1967 Dehn 191/ n K. Weiffenbach PrimaryExaminer-Cam Attorney, Agent, or Firmrnest F. Marmorek ducting pe minumh ferrous and like materials.

8 Claims, 1 Drawing Figure [75] Inventors: Tibor Kugler, Th gen; HansWolfhart Rieger, 'ngen, both of Switzerland I [73] Assignee: SwissAluminium Ltd., Chippis,

Switzerland [22] Filed: July 27, 1972 [21] Appl. No.: 275,517

[30] Foreign Application Priority Data July 29, 1971 Switzerland[1216/71 [52] US. Cl. 117/217, 29/624, 117/71 M,

117/93.3 117/131 7/227, 117/ 117/ .2,191/ DM, 191/29 [51] Int. 844dl/16, B44d 1/18 [58] Fiel Search 117/217, 71 M, 131, 105.2, 117/93.3 PF,227, 230; 29/624, 527.3, 52

191/22 DM, 23 R, 29 DM, 2

[56] References Cited UNITED STATES PATENTS 3,077,659 2/1963 Holzwarthet a1. ll7/105.2

METHOD OF MANUFACTURE OF A CONDUCTOR RAIL Reference is had to co-pendingapplications Ser. No. 275,518 filed July 27, 1972 and Ser. No. 275,519filed July 27, I972.

The present invention relates to a method of manufacture of a conductorrail, consisting of a body of aluminum or an aluminum alloy with a layerof more wearresistant material arranged on the body and forming asliding surface. Such conductor rails serve for supply of energy to adevice, such as a locomotive, a elevator or similar electrically drivenapparatus.

Special mechanical and electrical requirements are placed on conductorrails of this kind, which cannot be without influence on the method ofmanufacture of the conductor rails. The mechanical requirements are of astatic and mechanical-technological kind, in that a conductor rail isrequired which is in the first place free of sag and in the second placeresistant to wear. Electrically in order to avoid an excessive number ofsupply points, a good conductivity of the article is indispensable. Bythe development of corresponding sectional extrusions one hasindependently of the material of the conductor rail substantial controlon the sag. However, from the requirements of resistance to wear withsimultaneous good conductivity for conductor rails certain problems ofoptimisation arise, because, especially with said composite bodies ofsteel and aluminum, the different physical properties of the materialsoppose one another. Thus steel has the necessary resistance to wear, buta poor conductivity, whereas the behaviour is the opposite withaluminum.

In the past there has been no lack of attempts to provide methods ofmanufacture of compound bodies of the kind mentioned, the products ofwhich will constitute a best possible compromise with reference to theproperties required. In general the known methods aim at the union ofapre-shaped steel sectional extrusion as a component resistant to wear,with an extruded static load bearing and electrically well conductingcomponent, e.g., of aluminum. The union occurs by introduction of asectional part consisting of a ferrous material into a correspondingrecess of the extrusion of nonferrous metal with the employment ofpressure and heat. For additional security of the connection, screws orrivets are also inserted in the composite body. It is also known to formthe component consisting of aluminum or its alloys in several parts, sothat the steel part can be tightened by means of fastening elementsbetween the individual parts of aluminum. Finally there is in the stateof the art a method that envisages the rolling in of aluminum underpressure and elevated temperature in a load-bearing section extrusionconsisting of steel.

All these methods have disadvantages, in that they require a largetechnical expenditure, which lies in at least two press tools anddevices for uniting the extrusions, great costs for labour for handlingfastening means such as screws or rivets, and special rolling deviceswith heating arrangements.

In addition the composite bodies manufactured by the known methods arelimited in employment as conductor rails because of deficiencies. Thusthe components of the composite body formed as wearing parts take up alarge part of the total volume of the conductor rail, with theconsequence that the current must travel relatively long paths in apoorly conducting material to reach the pick-up surface. Furthermore inthis way joints of large area are formed between the loadbearing andwear-resisting components, which form a high internal resistance. Afurther disadvantage which has hitherto been unavoidable, is inherent ina product of manufacture which is formed with the help of pressure andheat or with employment of heat alone, thus for example by pressing ofaluminum onto a steel body at elevated temperature or casting ofaluminum into a steel body. In the union of metals of the kindmentioned, this is also true for the union of copper or its alloys withsteel, there is formed at the engaging surfaces of the metals a layer ofintermetallic compounds. These intermetallic compounds are brittle,electrically poorly conducting, and in particular the layer is notstable in its size, but continuously increases, because by means of itan electrical resistance is produced which develops heat, while itsgrowth with rising layer thickness rapidly increases. The inventionstarts from this and has set itself the task to provide a method ofmanufacture of a conductor rail, the product of which shows optimummechanical and electrical characteristics such as resistance to wear andelectrical conductivity, and the task is solved by a method ofmanufacture of a conductor rail consisting of a body of aluminum or analuminum alloy on which is a layer of a second material more resistantto wear in which method the second material is applied while it is inits liquid condition and simultaneously the heat content is carried awaythrough the body.

To avoid the formation of the intermetallic layer, the invention, incontrast to the teaching of the state of the art, sets out to make themost of the good thermal conductivity of the aluminum body for adeliberate forced carrying away the heat content of the layer of wearresistant material which is applied as liquid. The aluminum body isready formed previously. It is coated with metal only in the placeswhere necessary. By the term deliberate forced carrying away the heatcontent there is to be understood the maintenance of the bodytemperature before application of the coating of wearresistant material,even with introduction of auxiliary means. The wear-resistant materialcan, for formation of the sliding surface, be cast, or applied by flamespraying or spray welding. It is preferred to melt the wear-resistantmaterial in an arc and to apply it onto the aluminum body by means of aplasma jet. The method which is known under the term plasma spraying"for coating of turbine blades and the like has, for avoidance ofintermetallic intermediate layers in the manufacture of conductor railsof material of the kind mentioned, the special advantage that locallysharply defined heat can be introduced into the aluminum body with theconsequence of good removal on account of the remaining great crosssections with their favourable temperature gradients.

If the removal of heat produces special pproblems, or if formetallurgical considerations it is not advisable, then the methodaccording to the invention is furthermore advantageously carried out, inthat before application of the wear-resistant material on thecorresponding surface of the body, an intermediate layer is appliedwhich has good adhesion on the body and on the wear-resistant materialand hinders diffusion of the wear-resistant material into the body orvice versa, whereby the intermediate layer advantageously consists ofnickel, or a nickel-aluminum alloy, of tin, zinc,

silver, copper or alloys of these metals, and which, in accordance withthe thermal or other requirements should have a thickness of 5 'to 300p,and according to a further development provision is made to melt thematerials of the intermediate layer in an arc and to apply them by meansof a plasmajet which is an ionised carrier gas stream. According to theinvention materials are used for the intermediate layer which do notmake brittle intermetallic compounds either with the wear-resistantmaterial, i.e., steel, nor with the electrically well-conductingaluminum.

Below, by way of an example the method according to the invention willbe explained more closely by means of a product of said method.

FIG. 1 shows a sectional extrusion of aluminum intended for formation ofa conductor rail 10, which consists of a box-shaped hollow section 11and a T-section 12 connected with the box-shaped hollow section 11. Thebox-shaped hollow section 11 has three sides 13, 14, 15 suitable forpick-up of current, each of which as required carry a layer ofwear-resisting material 19. The flange 17 is intended for mounting ofthe conductor rail at both sides. According to the shape or arrangementof the pick-up 18, the current flowing through the conductor rail 10 istaken up either from the side 13, the sides 13 and 14, the side 15, orcombinations of them. By reason of the frictional engagement between thepick-up 18 consisting of a wear-resistant material and the conductorrail made of aluminum or its alloys, the latter would be subjected to arapid alteration of dimension by reason of the insufficient resistanceto wear for this purpose, which alteration would endanger a requiredsubstantially air-free transfer between conductor'rail 10 and pickup 18.The layer 19 of wear-resistant material connected to the sides l3, l4and provides a remedy against this alteration. The layer 19 consistssuitably of a ferrous alloy such as steel. It can however also consistof an alloy of the metals nickel, chromium, or copper, with such metals,which provides for the layer the required resistance to wear.

The layer 19 is applied in liquid condition to the sides, 13, 14, 15with simultaneous rapid removal of heat, to avoid the formation of anintermetallic layer of for example steel and aluminum. During saidforced heat removal there is transfered heat from the layer to a thirdmedium in contact with the body in such amount until the heat content ofthe layer is equal to that of the body and the transfer is performed soquickly that no increase in heat content of the body is noticible.According to one kind of coating, the sides 13, 14, 15 can be cast outof the wear-resisting material, in doing which it is suitable to carryout the application layer by layer, that is to say in individually thinlayers with simultaneous good distribution of the liquid material overthe sides 13, 14 and 15. To produce as great as possible a heat gradientand so that the requirement of rapid removal of heat is satisfied, whichas already indicated includes a maintenance of the conductor railtemperature as at the beginning of the casting process, the conductorcan in addition be cooled.

Flame spraying or spray welding are similarly suitable methods forapplication of the wear-resistant layer 19 in liquid form, which permitan even better distribution of the liquid with simplified additionalprovisions such as molding means in case of casting. Especially goodresults concerning the adhesion of the applied layer 19 on thecorresponding surfaces of the conductor rail 10 and with reference to assmall as possible an electrical transfer resistance between each layer19 and the conductor rail 10 are obtained, if the material of the layer19 is applied by means of a plasma spray pistol. in this connection thematerial of the layer 19 is melted in an arc, the material beinggenerally supplied in powder from to the are burning in the spray pistoland is conveyed under high pressure in the direction out of the spraypistol onto the conductor rail 10, by means of an ionised carrier gassupplied to the spray pistol, which can be an inert gas or alsodisassociated water ionised into its constituents. With this therearises a locally sharply defined zone of high heat application, whilethe remaining volume of the body aids for rapid removal of the heatapplication with practical exclusion of formation of an intermetalliclayer. In the same way a reliable breaking up of the aluminum oxidelayer at the instantaneous application point is achieved, whereby by thesimultaneous coating a possible reformation of the oxide layer issuppressed.

If the production of a strong temperature gradient gives rise to doubtsof a constructional or metallurgical nature, there can be applied firstto the corresponding sides 13, 14, 15, before the application of theliquid material of the layer 19, an intermediate layer 20 which has goodadhesion to the body, i.e., to the conductor rail 10 and to the layersof wear-resistant material, and which hinders diffusion of thewear-resistant material into the body or vice versa, which can consistof nickel, of a nickel-aluminum alloy, of tin, zinc, silver, copper, oralloys of these metals. These metals form, with the aluminum body andthe material of the wear-resistant layer 19, intermetallic compounds,which in contrast to one of aluminum and iron or one of their alloys,are not however brittle and electrically poorly conducting. Thethickness of the intermediate layer 20, which can amount to between51.1. and 300p, conforms substantially to the requirements of thewear-resistant layer 19, such as life with 'pre-determined coefficientsof friction and frequency of rubbing operations, permissible tolerancesof layer thickness, etc, which substantially call for the thickness ofthe layer 19.

With increasing thickness of the layers the thermal stresses upon thecomposite structure resulting from environmental influences willincrease and thus the intermetallic connection mechanism must be able topick-up and reduce these stresses.

The lowering of thermal stresses or tensions on the ground of externalinfluences and also those brought about by coating is further supported,in that the intermediate layer 20 has pores.

The materials of the intermediate layer are, in a possible embodiment ofthe method, melted in an arc and applied by a plasma jet onto thecorresponding sides 13, 14, 15, cooperating with the pick-up 18. Sincethese materials form no intermetallic compounds, which could disturbconduction of current, suitable considerations of manufacture, such as arational assembly, simplification of the expenditure on apparatus etc.,call for this mode of application. in addition it has appearedsurprisingly that, by the application of the wear-resistant layer bymeans of a plasma jet, the thickness of the layer to achieve the samelife as those produced according to the remaining methods, can bereduced by reason of its increased resistance to frictional wear despitethe same material composition, as used for the remaining methods. Undercertain conditions the wear-resistant layers produced according to theinvention should subsequently be ground. The danger of a local formationof cells favouring corrosion is counteracted, in that on the narrowsides of the layers which are exposed to the surrounding atmospheresealings can be applied.

Suitably the layers of wear-resistant material is applied in a thicknessof 0.3 to 2 mm.

What weclaim is:

1. Method of manufacture of a conductor rail consisting of a body ofaluminum or an aluminum alloy on which is a layer of a more resistant towear material selected from an alloy of a metal of the group consistingof iron, nickel, chromium, and copper in which method the material isapplied while it is in its liquid state, and simultaneously the heatcontent of the material is carried away through the body.

2. Method according to claim 1, wherein the material 18 cast.

3. Method according to claim 1, wherein the material is applied by flamespraying.

4. Method according to claim 1, wherein the material is applied meltedin an are by means of a plasma jet.

5. Method according to claim 1 wherein before the application of thematerial on the surfaces of the body intended for the pick-up ofelectrical current, an intermediate layer is applied which has goodadhesion to the body and to the material and hinders diffusion of thematerial into the body and vice versa.

6. Method according to claim 5, wherein the intermediate layer is of ametal selected from the group consisting of nickel, nickel-aluminumalloy, tin, zinc, silver, copper and alloys thereof.

7. Method according to claim 5, wherein the intermediate layer isapplied in a thickness of 5,u to 300p.

8. Method according to claim 5 wherein the material of the intermediatelayer is applied in a melted state by means of a plasma jet.

2. Method according to claim 1, wherein the material is cast.
 3. Methodaccording to claim 1, wherein the material is applied by flame spraying.4. Method according to claim 1, wherein the material is applied meltedin an arc by means of a plasma jet.
 5. Method according to claim 1wherein before the application of the material on the surfaces of thebody intended for the pick-up of electrical current, an intermediatelayer is applied which has good adhesion to the body and to the materialand hinders diffusion of the material into the body and vice versa. 6.Method according to claim 5, wherein the intermediate layer is of ametal selected from the group consisting of nickel, nickel-aluminumalloy, tin, zinc, silver, copper and alloys thereof.
 7. Method accordingto claim 5, wherein the intermediate layer is applied in a thickness of5 Mu to 300 Mu .
 8. Method according to claim 5 wherein the material ofthe intermediate layer is applied in a melted state by means of a plasmajet.